The von Hippel-Lindau (VHL) syndrome is a familial cancer syndrome characterized by the development of retinal angiomata, cerebellar hemangioblastomas, renal carcinomas, and pheochromocytomas,. A partial cDNA for the VHL gene was isolated by Michael Lerman and coworkers in 1993 and appears to be altered in both sporadic and inherited forms of renal carcinoma. The goals of this project are to gain mechanistic insights into the function(s) of the VHL protein (pVHL) and to understand how the loss of those function(s) contribute to neoplasia. Monoclonal antibodies will be raised against the VHL protein to facilitate studies of pVHL in vivo. The investigators have recently demonstrated that reintroduction of a wild (wt), but not a mutant, pVHL into renal carcinoma cells which lack endogenous wt pVHL suppressed their ability to form tumors in nude mice. A second goal of this proposal is to further refine the nude mouse assay and, if possible, develop cell culture based assays for pVHL function. In addition, two cellular proteins, p14 and p18 have been identified, which bind specifically to a 15 residue sequence in pVHL which is frequently altered by naturally occurring, presumed loss of function, VHL gene mutations. This raises the possibility that binding to p14 and p18 is necessary, and perhaps even sufficient, for tumor suppression by pVHL. To test this hypothesis, it will be asked whether specifically engineered pVHL mutants which do or do not bind to p14/p18 can suppress tumor cell growth in the nude mouse assay and, if such assays can be developed, in cell culture. In addition peptide microsequence data for p18 has been obtained and it appears to be a novel protein. The plan is to clone the cDNAs for p15 and p18, using classical reverse genetics, in hopes that their identities may provide insights into pVHL function. Furthermore, these cDNAs will likely be invaluable reagents for further exploring the functional significance of pVHL binding to these two proteins.